This requires maintaining the highest standards of security, durability, integrity, and availability—with systems correctness serving as the cornerstone for achieving these priorities. Second, we gained the deep understanding and confidence needed to implement aggressive performance optimizations while maintaining systems correctness. This systematic approach toward systems correctness has become a force multiplier at AWS’s scale, enabling faster development cycles through improved developer velocity while delivering more cost-effective services to customers. Lightweight Formal Methods Another way that AWS has brought formal methods closer to its engineering teams is through the adoption of lightweight formal methods. Continuous fuzzing, especially coverage-guided scalable test-input generation, is also effective for testing systems correctness at integration time.